Block copolymers of polycarbonates including segments of other polymers have been known, see for example, Goldberg, U.S. Pat. No. 3,030,335, Adelmann, et al., U.S. Pat. No. 4,252,922, and Behnke et al., U.S. Pat. No. 4,436,839 who disclose block copolymers of bisphenol-A carbonates including segments derived from polyalkylene glycols. In Schreckenberg et al, U.S. Pat. No. 4,217,437, the polyalkylene glycols are advantageously end-functionalized, e.g., with diphenol carbonates. Such block copolymers are useful per se as film frames and shaped articles because of toughness conferred on the polycarbonates by the segments of other polymers. The block copolymers can also be blended with polycarbonate resin, and a whole host of other thermoplastic addition and condensation polymers to provide thermoplastic molding compositions showing markedly improved resilience properties compared with the unblended resins.
It is also known that a highly useful family of heat resistant thermoplastic polymers is comprised of polyetherimide resins made by reacting a bis ether anhydride and an aromatic diamine. See, for example, Williams III, et al, U.S. Pat. No. 3,983,093, who discloses the reaction product of 2,2-bis[4-2,3-dicarboxyphenoxy phenyl] propane dianhydrid (BPA-DA) and metaphenylene diamine. The linear polymer is terminated with amino groups, and has a very high molecular weight and high glass transition temperature (Tg, typically=216.degree. C.). Such a material cannot be readily blended with aromatic polycarbonate, because mixtures with two Tg's are obtained, one for the polyetherimide resin, and one for the polycarbonate. Furthermore because of the amino terminal groups, polyetherimides cannot be successfully used as blocks in copolymers with aromatic polycarbonate segments, as is done with polyethers. Moreover, no method is known in the art to functionalize high molecular weight polyetherimide resins to accommodate their introduction as blocks into resin copolymers, and even if there were such methods, the length of the segments would probably be too high to provide a composition that would thermoform readily in conventional equipment.
It has now been found that an entirely new approach will solve the above-mentioned problems, and this is the subject matter of the present invention. If polyetherimides are prepared from conventional ingredients in the presence of significant amounts of arylaminoalcohols there will be surprisingly obtained polyetherimide oligomers which are end functionalized with hydroxyl groups. In contrast to known polyether imides, such materials will have low intrinsic viscosities, low to moderate molecular weights and high hydroxyl equivalent weights. Moreover, they have been surprisingly found to be uniquely suitable for preparing block copolymers. For example, as is disclosed in the concurrently filed application of E. N. Peters, Ser. No. 784,511, the copolymers prepared by reacting the hydroxy-terminated polyether imide oligomers of the present application with bisphenol-A and a carbonate precursor exhibit only one glass transition temperature Tg, and have a high intrinsic viscosity, making them useful as engineering thermoplastics and in blends with other resins.